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UNIVERSITY  OF  ILLINOIS. 

Agricultural  Experiment  Station, 

CHAMPAIGN,  APRIL,  1894. 


BULLETIN  NO.  32. 


AN  ACID  TEST  OF  CREAM. 

The  sourness  of  cream  is  one  of  the  things  considered  by  many 
dairymen  in  making  butter.  They  may  not  agree  on  the  amount  of 
acidity  that  cream  should  have  when  it  is  ready  for  churning,  but  many 
base  their  judgment  on  the  taste  or  appearance  of  the  cream. 

The  first  record  of  a  measurement  of  the  acidity  of  cream  before 
churning,  so  far  as  known  to  the  writer,  was  reported  in  1887  by  John 
Sebelein,  in  Versuchs-Stationen,  XXXIV,  p.  94.  He  used  an  alkaline 
liquid  of  known  strength  (one-tenth  normal)  and  by  adding  a  few  drops 
of  a  liquid  indicator,  phenolphtalein,  to  a  measured  quantity  of  cream 
(50  c.  c.,  or  about  one-tenth  of  a  pint)  the  amount  of  acid  in  the  cream 
was  estimated  by  measuring  the  quantity  of  the  alkaline  liquid  that  it 
was  necessary  to  add  to  the  50  c.  c.  of  cream  in  order  to  produce  a  pink 
color  in  the  cream  tested.  The  indicator,  phenolphtalein,  has  the  prop- 
erty of  causing  a  pink  color  in  some  alkaline  liquids,  but  does  not  change 
the  color  of  acid  solutions.  This  gives  a  means  of  measuring  the 
amount  of  acid  in  milk  or  cream  by  noting  the  quantity  of  an  alkaline 
liquid  of  known  strength  that  will  produce  this  pink  color  in  a  measured 
amount  of  cream.  The  strength  of  the  alkaline  liquid  and  the  amount 
of  cream  taken  for  each  test  are  constant,  known  quantities,  always  the 
same  in  comparative  trials  of  different  lots  of  cream.  The  amount  of 
acid  in  the  measured  quantity  of  cream  is  unknown  until,  by  testing,  it 
is  observed  how  much  of  the  standard  alkaline  liquid  it  is  necessary  to 
use  to  produce  the  pink  color.  A  one-tenth  normal  solution  of  an 
alkali  is  of  a  definite  strength  understood  by  chemists.  The  alkali  may 
be  caustic  soda,  potash,  lime,  or  baryta.  All  these  are  efficient  and  re- 
sults will  be  comparable,  if  a  one-tenth  normal  solution  of  any  one  of  them 
is  used. 

389 


390  BULLETIN    NO.    $2. 

In  the  fall  of  1889  this  method  of  testing  the  acidity  of  cream  was 
used  by  Dr.  Manns,  at  the  creamery  of  Gurler  Bros.,  DeKalb,  111.,  and 
also  in  churnings  of  cream  which  he  made  at  this  Station.  He  found 
that  when  cream  was  churned  at  a  temprature  of  58°  to  62°  F.  too 
much  acid  in  the  cream  injured  the  quality  of  the  butter,  and  too  sweet 
cream  churned  at  this  temperature  caused  a  loss  of  butter  in  the  butter 
milk.  The  butter  was  not  all  churned  out  unless  the  cream  was  suffi- 
ciently soured.  The  butter  was  of  poor  quality  if  the  cream  was  too 
sour.  These  trials  indicated  that,  so  far  as  the  acidity  of  the  cream  had 
an  influence  on  the  flavor  of  the  butter  and  on  the  thoroughness  of  the 
churning  at  58°  to  62°,  the  best  results  were  obtained  when  the  acidity 
of  50  c.  c.  of  cream  was  neutralized  by  about  40  c.  c.  of  one-tenth  nor- 
mal alkali.  This  work  was  published  in  bulletin  No.  9,  of  this  Station, 
May,  1890.  The  "per  cent  of  acidity"  as  given  in  that  bulletin  can  be 
converted  into  c.  c.  of  one-tenth  normal  alkali  by  multiplying  the  "per 
cent  of  acidity"  by  5,000  and  dividing  by  87. 

A  Chicago  dealer  in  dairy  supplies  put  on  the  market  the  necessary 
outfit  for  testing  the  acidity  of  cream  by  the  method  already  described, 
under  the  name  of  "Manns  acid  test."  The  apparatus  is  sold  for  $5.00 
and  the  "neutralizer,"  or  one-tenth  normal  alkaline  liquid,  at  $1.00  per 
gallon.  This  amount  of  the  liquid  ought  to  make  about  100  tests  of  cream. 
The  liquid  itself  is  not  expensive,  but  its  exact  strength  must  be  accu- 
rately determined  by  a  person  who  has  the  necessary  apparatus  for  test- 
ing it.  In  order  to  use  this  test  it  is  also  necessary  to  have  a  burette  for 
measuring  the  alkaline  liquid,  a  pipette  for  measuring  the  cream,  and  an 
alcoholic  solution  of  phenolphtalein.  The  necessary  manipulations  in 
using  the  test  are  simple  and  the  method  has  given  good  satisfaction  to 
the  writer  and  others  in  practical  dairy  work.  The  same  amount  of 
acidity  in  cream  may  not  be  universally  adopted,  but  no  one  wants 
cream  to  sour  until  it  spoils  the  flavor  of  the  butter. 

This  acid  test  of  cream  has  been  extensively  used  by  Gurler  Bros., 
and  at  other  places.  Since  it  was  first  introduced,  Mr.  H.  B.  Gurler 
observed  that  the  exhaustiveness  of  churning,  or  the  complete  separa- 
tion of  all  the  butter  from  the  cream  by  churning,  was  largely  influenced 
by  the  temperature  at  which  cream  was  churned  rather  than  by  the 
acidity  of  the  cream.  The  practice  in  his  creameries  during  the  past 
year  or  more  has  been  to  churn  thick  separator  cream,  contained  25  to 
35  per  cent  of  fat,  at  a  temperature  of  45°  to  55°  F.,  usually  about  52°  F. 
This  is  the  temperature  of  the  buttermilk  when  drawn  from  the  churn 
immediately  after  the  butter  "comes,"  and  not  always  the  temperature  of 
the  cream  when  it  is  put  into  the  churn.  If  the  churning  is  done  in  a 
warm  or  cold  room  the  temperature  of  the  cream  will  gradually 
attain  the  temperature  of  this  room,  although  it  may  have  been  warmer 
or  cooler  than  the  room  when  it  was  put  into  the  churn,  so  that  the  tem- 
perature of  each  churning  is  the  temperature  at  which  the  butter  comes. 

When  cream  is  obtained  by  the  gravity  processes  of  setting  milk,  it 


1894-]  AN    ACID    TEST    OF    CREAM.  39! 

does  not  often  contain  much  over  15  per  cent  of  fat.  Such  cream  is 
ordinarily  too  thin  to  be  churned  at  this  low  temperature,  but  must  be 
ripened  and  churned  at  about  62°  F.  The  best  separators,  however,  can 
be  so  regulated  as  to  give  cream  of  a  desired  thickness  and  at  the  same 
time  skim  the  milk  so  thoroughly  that  only  a  trace  of  fat  is  left  in  the 
skim  milk. 

It  has  been  found  by  Mr.  Gurler  in  his  practice  and  by  observations 
made  by  the  writer  at  his  creameries,  that  thick  cream  containing  about 
30  per  cent  fat  can  be  churned  at  about  52°  F.,  so  that  there  is  only  a 
trace  of  fat  left  in  the  buttermilk.  This  shows  that  under  proper  con- 
ditions the  churn  can  be  made  to  do  as  efficient  work  as  the  separator, 
and  that  within  certain  limits,  the  thickness  of  the  cream  and  the 
temperature  at  which  it  is  churned  have  more  influence  on  the  exhaus- 
tiveness  of  churning  than  does  the  acidity  or  sourness  of  the  cream, 
Although  this  is  true,  an  acid  test  of  cream  can  be  of  great  practical 
value  especially  for  the  purpose  of  indicating  the  proper  degree  of  ripe- 
ness of  cream  to  be  churned ;  for  if  cream  continues  to  ripen  after  it  has 
reached  a  certain  amount  of  acidity,  another  kind  of  fermentation  seems 
to  take  place  which  injures  the  quality  of  the  butter. 

The  fermentation  or  souring  of  cream  is  caused  by  bacteria.  These 
are  plants  which  are  seen  only  by  the  aid  of  a  powerful  microscope. 
They  multiply  amazingly  fast  when  kept  at  the  proper  temperature. 
Among  plants  which  we  can  see  without  any  microscope  there  are  cer- 
tain varieties  which  we  call  weeds.  If  weed  seeds  are  in  the  soil  they 
grow  as  well  as  the  good  seed  which  we  plant.  The  same  thing  is  true 
of  the  microscopic  plants,  bacteria.  There  are  some  which  we  are  as 
anxious  to  keep  out  of  cream  as  we  are  to  prevent  the  growth  of  weeds 
in  a  corn  field,  and  there  are  others  which  at  present  are  considered  to 
be  the  agents  in  producing  a  fine  flavor  in  butter. 

Dirt  is  the  source  of  most  all  "bad"  bacteria  which  find  their  way 
into  milk,  cream,  and  butter.  If  everything  was  clean  through  which 
the  milk  passes,  from  cow  to  caddy  of  butter,  it  would  be  a  compara- 
tively easy  matter  to  plant  a  pure  culture  of  bacteria  in  cream,  and  get 
that  ferment  alone,  or  in  large  excess  over  all  others;  but,  like  weed 
seeds  in  soil,  we  have  to  contend  with  bad  bacteria,  which  grow  up  and 
choke  the  good  seed  and  all  the  superior  qualities  thereof. 

If  great  care  were  taken  to  keep  the  cows  clean,  the  milker  clean, 
and  the  milk  dishes  clean,  there  would  be  a  greater  certainty  of  produc- 
ing a  high  flavored  and  high  priced  butter,  because  there  are  fewer 
weed  seed  bacteria  in  clean  milk  and  cream. 

The  rate  at  which  cream  ripens  in  ordinary  practice  is  not  often 
uniform.  It  is  not  only  influenced  by  the  cleanliness  of  the  milker  and 
dairyman,  as  mentioned  above;  but  the  weather,  the  temperature  at 
which  the  cream  is  set  for  ripening^  and  the  amount  of  fat  in  the  cream 
also  influence  the  rapidity  of  souring.  Hot  or  warm,  muggy  weather 
has  a  tendency  to  hasten  souring,  while  a  clear,  bright  atmosphere,  as 


392  BULLETIN    NO.    32. 

well  as  cold,  are  not  so  favorable  for  the  growth  of  the  bacteria  which 
cause  cream  to  sour. 

Since1  it  is  the  milk  sugar  that  ferments  when  cream  sours,  it  is 
obvious  that  thin  cream,  with  only  ten  to  fifteen  per  cent  of  fat,  contains 
more  milk  sugar  and  will  sour  faster  than  rich  cream  which  contains 
more  fat  and  consequently  less  milk  sugar  and  casein. 

These  uncertain  quantities,  cleanliness,  weather,  and  richness  of  the 
cream,  which  all  have  an  influence  on  the  rate  at  which  cream  sours, 
show  the  value  of  some  simple  test  to  indicate  the  amount  of  acidity 
in  cream  for  churning;  for,  as  said  above,  after  cream  has  soured 
to  a  certain  point,  another  kind  of  fermentation  takes  place  that  injures 
the  quality  of  the  butter. 

A  simple  test  that  will  indicate  the  amount  of  acid  in  cream  can  be 
used  to  show  when  cream  is  sour  enough  to  suit  the  standard  adopted 
by  different  men  and  markets.  A  uniformity  in  the  sourness  can  thus 
be  obtained  by  churning  each  lot  of  cream  when  the  test  shows  a  certain 
amount  of  acidity,  and  no  lot  of  cream  need  spoil  from  over  ripeness,  as 
the  test  will  show  when  the  danger  point  is  near. 

In  following  up  this  line  of  work  the  writer  has  developed  a 
method  of 

CREAM  TESTING  WITH  ALKALINE  TABLETS. 

A  formula  has  been  worked  out  by  which  a  definite  amount  of  solid 
alkali  can  be  made  into  a  tablet  containing  both  the  alkali  and  the  indi- 
cator necessary  for  testing  the  acidity  of  cream  or  milk. 

Each  tablet  contains  a  definite  amount  of  alkali  which  will  neutral- 
ize as  much  acid  as  4.66  c.  c.  of  a  one-tenth  normal  alkaline  liquid.  A 
test  of  a  number  of  the  tablets  showed  them  to  be  very  uniform  in  the 
amount  of  alkali  contained  in  each  tablet.  The  extreme  difference 
amounted  to  three-tenths  of  one  c.  c.  of  the  one-tenth  normal  liquid. 
One  thousand  tablets  weigh  about  twelve  ounces.  Each  tablet  is  about 
three-eighths  of  an  inch  in  diameter  and  one-eighth  inch  thick,  and  they 
can  be  used  instead  of  the  one-tenth  normal  alkaline  liquid  and  the 
liquid  indicator  mentioned  on  page  390. 

The  tablets  can  be  used  for  testing  the  acidity  of  cream  in  the  fol- 
lowing way: 

DISSOLVING  THE  TABLETS. 

Label  several  clean  4  or  6  oz.  white  glass  bottles,  No.  i,  No.  2, 
No.  3,  etc.  Put  one  tablet  into  each  of  the  bottles  numbered  i ; 
two  into  each  numbered  2 ;  and  three  into  each  bottle  numbered  3,  etc. 

The  bottles  can  be  labeled  by  roughening  a  place  on  the  side  of 
the  bottle  with  a  wet  file.  The  number  can  be  marked  with  a  lead 
pencil  on  this  rough  surface. 

Add  to  each  bottle  enough  clean,  soft  water  to  completely  cover 
the  tablets  and  let  them  stand  until  the  tablets  are  all  dissolved.  They 


1894-]  AN    ACID    TEST    OF    CREAM.  393 

will  dissolve  faster  in  hot  than  in  cold  water.  If  the  solution  of  the 
tablets  is  hastened  by  shaking  the  bottle  or  stirring  the  liquid,  it  should 
be  done  in  such  a  way  as  to  prevent  any  loss.  As  they  do  not  dissolve 
immediately  they  should  be  put  to  soak  about  one-half  hour  before  the 
cream  is  to  be  tested.  The  strength  of  the  solution  does  not  change 
perceptibly  by  standing  four  or  five  hours,  but  there  is  some  change  in 
a  tablet  solution  which  is  a  day  or  more  old.  The  solid  tablet  will  not 
change,  and  the  only  precaution  necessary  is  to  use  a  fresh  solution  of 
the  tablets  in  testing  the  acidity  of  cream.  Excepting  the  flocculent 
residue  or  settlings,  which  will  not  dissolve  in  water,  the  tablets  should 
all  disappear  in  the  solution  before  it  is  added  to  the  cream  to  be  tested. 
When  the  solution  is  complete  the  bottles  contain  a  reddish  colored 
liquid,  the  alkaline  strength  of  which  is  indicated  by  the  number  on  the 
label  of  the  bottle  that  shows  how  many  tablets  were  put  into  each 
bottle. 

TESTING  THE  CREAM. 

The  cream  to  be  tested  should  be  thoroughly  mixed.  Then  meas- 
ure 25  c.  c.  of  the  cream  into  a  glass  tumbler  or  a  cup.  If  the  cream  is 
very  thick,  25  c.  c.  of  clean  rain  water  may  be  mixed  with  it  in  the  dish. 
The  sourness  of  the  cream  is  then  ascertained  by  adding  the  reddish  col- 
ored solution  of  the  tablets  to  this  measured  quantity  of  cream  until  it 
retains  a  pinkish  color.  When  the  two  liquids,  cream  and  tablet  solu- 
tion, are  thoroughly  mixed,  the  pink  color  does  not  remain  permanent 
until  the  acid  of  the  cream  is  completely  neutralized  by  the  alkali  of  the 
tablets.  An  excess  of  the  alkali  causes  the  color  to  increase.  The 
acidity  of  the  cream  is  measured  by  adding  just  enough  of  the  alkali  to 
produce  a  permanent  change  of  color  from  white  to  pink.  No  further 
addition  of  the  alkali  is  necessary,  as  the  first  change  of  color  indicates 
the  point  when  the  acid  is  all  neutralized.  A  piece  of  white  paper 
placed  under  the  tumbler  in  which  the  cream  is  tested  will  help  to  show 
the  change  of  color.  It  will  be  found  to  be  more  accurate  to  adopt  as 
the  end  of  the  test  the  point  when  the  first  change  of  color  appears  and 
the  cream  is  no  longer  white,  rather  than  to  try  to  get  a  certain  shade 
of  pink  color  every  time. 

The  amount  of  alkali  required  to  produce  this  change  of  color 
shows  the  sourness  of  the  cream  as  indicated  by  this  test.  A  change  of 
color  may  be  produced  in  25  c.  c.  of  sweet  cream,  by  a  solution  of  one 
or  two  tablets.  As  the  sourness  of  the  cream  increases,  25  c.  c.  of  it 
may  require  a  solution  of  three,  four,  or  five  tablets  to  change  the  color. 

The  indications  are  that  a  cream  which  requires  a  solution  of  six  or 
more  tablets  to  change  its  color  is  too  sour.  The  butter  made  from 
such  cream  will  be  "  off  flavor."  The  only  general  direction  that  can 
now  be  given  as  applicable  to  nearly  all  cream,  is  to  churn  it  when  25 
c.  c.  of  the  thoroughly  mixed  cream  is  not  colored  by  a  solution  of  four 
tablets  but  is  decidedly  colored  by  a  solution  of  five  tablets. 


394  BULLETIN  NO.  32.  [April,  1894. 

Some  dairymen  may  prefer  to  churn  a  less  acid  cream  and  adopt 
the  sourness  of  cream  which  will  give  a  color  with  a  solution  of  three 
tablets. 

Comparative  trials  made  by  each  person  of  the  acidity  of  the  cream 
and  the  flavor  of  the  butter  made  from  it  will  be  a  satisfactory  guide  to 
follow. 

This  test  will  show  the  sourness  of  each  lot  of  cream  so  that  a  uni- 
formity of  acidity  can  be  had  in  each  churning.  How  much  acidity 
each  lot  of  cream  should  have,  or  whether  cream  should  be  churned 
sweet  or  sour,  may  be  a  matter  of  opinion  with  the  butter  maker.  This 
test  serves  as  an  aid  to  show  him  when  the  cream  is  of  the  sweet- 
ness or  sourness  which  he  prefers.  It  will  also  show  when  the  cream 
ought  to  be  churned  in  order  to  prevent  it  from  spoiling  the  butter  by 
ripening  too  far  and  becoming  too  sour  for  the  best  results. 

These  tablets  are  made  by  Charles  S.  Baker  &  Co.,  Grand  Cross- 
ing, Chicago,  Illinois.  The  complete  outfit,  including  one  thousand 
tablets  and  one  25  c.  c.  pipette,  costs  $2.50  delivered.  One  thousand 
tablets  ought  to  make  250  tests  of  cream. 

E.  H.  FARRINGTON,  M.  S.,  Chemist. 


All  communications  intended  for  the  Station  should  be  addressed, 
not  to  any  person,  but  to  the 

AGRICULTURAL  EXPERIMENT  STATION,  CHAMPAIGN,  ILLINOIS. 

The  bulletins  of  the  Experiment  Station  will  -be  sent  free  of  all 
charges  to  persons  engaged  in  farming  who  may  requ'est  that  they 
be  sent. 


UNIVERSITY  OF  ILLINOIS-URBANA 


